2021 Hyundai Sonata engine problems

Related recalls

No recalls on file.

What owners say

1. Filed Jun 24, 2026SCEngineFuel, Hybrid & EV Propulsion

   At approximately 130,000 miles, vehicle developed and internal coolant leak caused by a failed Exhaust Heat Recovery System (EHRS) in the center muffler assembly, matching TSB 23-EM-009H - a known manufacturing defect documented by Hyundai. Coolant has been slowly leaking internally into the exhaust system. The authorized Hyundai dealership initially failed to diagnose the internal leak and told me there was no leak and wanted to send me home. After pushing back, the…

   NHTSA complaint #11746137 · source
2. Filed Jun 1, 2026TNElectrical SystemEngine

   The car will idle high around 1200 rpms. The car will most of the times fix the issue when you turn the car off and back on but it will start again after driving. This is a known issue with the car. I have had the egr valve replaced since it will pop up the codes P240F and P049 for egr slow response and control position exceeded learning limit but the problem came back within two days. I did find a forum that deals with the joint connector repair but this needs to be a…

   NHTSA complaint #11741201 · source
3. Filed May 19, 2026140,000 miFLTowedEngineFuel, Hybrid & EV Propulsion

   The contact owns a 2021 Hyundai Sonata. The contact stated while driving at an undisclosed speed, the engine shuddered and the engine stalled. In addition, the engine seized. No warning lights were illuminated. The contact stated that the vehicle was seized in the middle of the road. The contact stated that while attempting to start the vehicle, the vehicle started. The failure reoccurred. The vehicle was towed to the residence. The vehicle was not diagnosed or repaired by…

   NHTSA complaint #11738864 · source
4. Filed Apr 14, 2026ALEngine

   The Exhaust Heat Recovery System (EHRS) has failed for the second time on this vehicle. The first failure occurred at approximately 35,000 miles and was repaired under Hyundai Technical Service Bulletin 23-EM-009H, which Hyundai issued to address this exact defect across 2020-2023 Sonata Hybrid models. The vehicle has now reached 71,000 miles and is experiencing the identical symptoms: coolant loss, overheating, and white exhaust smoke. The EHRS shares a coolant loop with…

   NHTSA complaint #11730992 · source
5. Filed Mar 26, 2026PAEngineFuel, Hybrid & EV PropulsionVisibility & Wipers

   The internal core of the Exhaust Heat Recovery System (EHRS), part of the center muffler/front pipe assembly (#28600-L5210), suffered a catastrophic failure. This allowed approximately 9 gallons of engine coolant to leak directly into the hot exhaust stream. Safety Risk: This failure creates a severe visibility hazard. During acceleration from stop lights and stop signs, the vehicle emits massive, thick clouds of white glycol smoke. The smoke is so dense that it completely…

   NHTSA complaint #11727380 · source
6. Filed Mar 17, 2026SCEngine

   Hyundai technical service bulletin 23-EM-009H (EHRS COOLANT LEAK) - AKA a faulty heat exchange that causes the coolant to leak into the exhaust and burn away. Resulting in a very hard to diagnose coolant disappearance. This should be a recall. They have literally already acknowledged a manufacturer defect with the service bulletin. The problem is that in most cases, it occurs out of the 60k or 100k warranty. The dealer seems to have discretion as to which of the mileage…

   NHTSA complaint #11725107 · source
7. Filed Feb 22, 2026GAEngineFuel, Hybrid & EV Propulsion

   On i believe 1/14/26, my check engine light came on. Scheduled appt.for 1/16/26 for diagnostic. Several things were wrong. I decided to come back due to not having the money at the time. Over the wked, I remembered a recall notice i received around November that I asked about in November during my oil change & was told the parts aren't in & they'd give me a call. Upon viewing the recall it seemed some things I was told on 1/16/26 could be a result of the recall. I called my…

   NHTSA complaint #11719681 · source
8. Filed Feb 20, 2026FLEngineVisibility & Wipers

   The EHRS coolant system failed and had a leak causing the coolant to be excessively burned off as thick white smoke. This caused me to not be able to see anything behind me and forced others to stop or slow down dramatically to avoid colliding with me. I had my engine overheat and force me to pull over on the side of an unsafe road because the exhaust system burned off my entire tank of coolant in less than a mile. I have taken this to a Hyundai dealership and they confirmed…

   NHTSA complaint #11719316 · source
9. Filed Feb 16, 2026MIEngineTransmission & Drivetrain

   Vehicle suddenly lost heat in 30 degree weather. No warnings, check engine light, or temperature gauge indicators came on. Lucky made it to a parts store and found out I was extremely low on coolant. Bought coolant and put it in. Made it back to the house and was immediately low again. No visible leaking. Oil was completely fine (1 gallon of coolant would have have left some kind indicator). Realized it was more than likely the ehrs. If this happened during the summer, my…

   NHTSA complaint #11718194 · source
10. Filed Jan 9, 2026ALDriver Assistance & Safety TechEngineSuspension

    Engine makes rattling and knocking noises. Transmission hesitates and jerks Suspension front struts and rear shocks are bad. Possible the isolators. Having horrible back pain when riding in car. Starter intermittently doesn't work Lane keep assistance goes over small bump in road will make car drive in opposite lane into on coming traffic. Took car to Tameron hyundai in Birmingham on the 29th of December 2025. Told them everything thats going on with the car. They did…

    NHTSA complaint #11709919 · source
11. Filed Jan 9, 2026FLEngineFuel, Hybrid & EV Propulsion

    I was driving my 2021 Hyundai Sonata at approximately 3:00 AM when the vehicle suddenly began shaking and vibrating. While stopped at a traffic light, the check engine light illuminated, and the engine was shaking severely. I immediately pulled over and shut off the engine. After waiting approximately one hour, I restarted the vehicle, but it was only able to drive very slowly. The following day, the vehicle was towed to a local repair shop. Diagnostic testing showed a…

    NHTSA complaint #11709821 · source
12. Filed Nov 8, 2025WAEngineOther / UnknownVisibility & Wipers

    The vehicle's HVAC (heating) system failed. It stopped producing heat on one side of the vehicle. My mechanic/dealer diagnosed the issue as a broken component within the HVAC case under the dashboard, requiring full dashboard removal and a repair estimated at over $3,000. This failure prevents the defroster from working properly, which is a major safety hazard as it cannot clear fog or frost from the windshield. A search of online forums and owner communities shows this is a…

    NHTSA complaint #11698349 · source

Source: U.S. National Highway Traffic Safety Administration (NHTSA) Office of Defects Investigation public data. Complaints are submitted by owners and are not verified by NHTSA or by us; a complaint does not prove a defect exists. View this vehicle on NHTSA.gov Methodology